I know that gurus cannot add covers to the site.

But at least
rockabilly1983's covers were usually added almost instantly (a day or two after he posted them to the forums). Which means they either got priotized or added without much of a thought.
So far only 32 covers have been added to the site in all of 2019. (Not counting dublicate entries / identical covers, that just have a different case format.) 7 are from admins, so were added without approval process. 14 are from
rockabilly1983 and 11 from others.
That makes 25 approved covers (at best) or 2,5 covers per cover admin in 8 month.
To be clear, I don't want to call anyone out. I am sure everyone has their reasons.

I just think blaming the upload cue is misleading. It suggests that you just have to wait a bit longer for your cover to be approved. (NOTE: It used to be 2 Weeks according to the FAQ.) But as it looks right now, even if the upload cue is just around 100 covers (and it is probably much more), you will be waiting for years...
So a more truthfull anwser would be, that you simply cannot contribute to the site at the moment.